One particularly desirable form of street sweeper is the recirculating air sweeper, in which dirt which has been disturbed by a brush passes into a cleaning head, and is drawn into a recirculating air flow pattern which conveys the dirt to a dust collector, and permits the air with reduced dirt and dust to recirculate back to the cleaning head. By this means, the street sweeper does not have a large air exhaust which, without a filter, would spew air with a certain amount of dust and dirt back onto the street. The volume of dirt and dust are so great that it is not practical to attempt to use any kind of a filter for the air stream, which would clog too rapidly.
In a typical cleaning head, recirculating air flows into an open-faced chamber with the open face directed downwardly to receive dirt from the street. The vigorously recirculating air enters the chamber, typically through a slot which extends most of the width thereof, while the recirculating air is drawn out of the chamber through an outlet port adjacent one end thereof.
It has been found that as dirt picks up a significant velocity in the chamber moving toward the outlet port, some of the dirt can fly right by the outlet port, falling out of the head along its side, resulting in incomplete dirt pickup. In an attempt to prevent this, a baffle has been made in a prior art design, being positioned between the side wall of the cleaning head and the outlet port to stop dust from flying laterally past the outlet port. However, even in this circumstance, dirt has been found to collect behind the baffle and then fall back to the street, so that under certain dirt pickup conditions, the street sweeper can leave a trail of dirt behind, resulting from dirt collecting and then falling out of the area behind the baffle relative to the outlet port.
By this invention, a cleaning head is modified to significantly reduce this problem, so that laterally moving dirt does not readily fly past the outlet port, but rather is stopped and sucked through the port with recirculating air. At the same time, dirt does not collect in large quantities behind the baffle of this invention, but rather is also sucked into the outlet port with recirculating air.